Wireless sensor networks typically include spatially distributed devices associated with sensors that remotely transmit and receive data over a network. The relayed information can be employed to monitor both physical and environmental conditions such as, for example, temperature, location, and pressure. Such wireless sensor networks can be powered by a variety of power sources such as a battery. Batteries are a cost effective, ubiquitous, and commonly known powering technology. The specific drawbacks of batteries, however, include finite lifetime, replacement cost, and disposal concerns. Additionally, sensor nodes tend to be portable and integrated with multi-functions; therefore, limited power issues, small size and integration capabilities pose additional problems to the effective implementation of a promising wireless sensor network.
Energy harvesting (or energy scavenging) provide a useful way to power electronic devices without the need for batteries or electrical wiring. Energy harvesting can be defined as the conversion of ambient energy (e.g., mechanical/vibration, thermal, light/radiation energy, etc.) into usable electrical energy. Several technologies exist to extract energy from the environment such as, for example, solar, thermal, kinetic energy, and vibration energy. Conventional energy harvesting devices utilize a linear harvester for generating electrical power from vibrations, oscillations or other mechanical motions. Linear oscillators, however, generate significant power within a narrow band around resonance and the power is limited by intrinsic damping factor and the driving force at resonant frequency. Such prior art devices implementing linear (resonant) oscillator have not been able to generate enough power density and only achieve 10-100 μW/cc or less at 0.5 g acceleration.
Based on the foregoing it is believed that a need exists for an improved nonlinear energy harvester apparatus and method with an optimal potential energy profile. A need also exists for an improved nonlinear oscillator apparatus and method for harvesting vibration energy, as described in greater detail herein.